Methylenecyclobutenes are synthesized via thermal conditions between allene ethers and alkyne and successfully transformed to other four-membered ring compounds. This strategy provides a series of methylenecyclobutenes in moderate yields with broad functional groups.

Abstract

Methylenecyclobutenes are useful precursors to provide other organic compounds. We report intermolecular [2+2] cycloaddition of allene ethers and alkynes at 100 °C, which gives methylenecyclobutenes in 50–60 % yields. The reaction does not require any metal catalyst and shows broad substrate scope, high regioselectivity and high stereoselectivity.